The atrial trabeculae of frog heart are favorable objects for the electrophysiological (voltage clamp) study of the genesis of action potentials in cardiac muscle. Previous work on this general subject has suffered from a number of uncertainties about the validity of the usual electrical measurements. Digital ssmulations of the behavior of electrial equivalent of trabeculae will be compared with the results of voltage clamp experiments to develop an adequate description of the kinetics of the conductance changes in this tissue. The dependence of the slow inward current on external sodium will be investigated. We will investigate the models of the ionic basis of the genesis of action potentials using computer simulations. The frog heart is also an ideal source for purifying first the plasma membrane of an excitable cell and second, isolating the component proteins. We will isolate proteins and recombine the phospholipids in artificial bilayers in order to provide simplified experimental models of the excitable cell membrane. Finally, we will test the effects of antibodies against these biochemical preparations on the electrical behavior of trabeculae.